As is known, in order to detect an intrusion into, or out of, a protected volumetric space, a sensor sheet is provided to enclose the volume of interest which has a continuous electrical or optical signal path disposed in the sheet and substantially encompassing the full extent thereof. An electrical signal, in the case of a wire path, or an optical signal, in the case of an optical fiber path, is introduced to one end of the signal path, and the signal is received at the opposite end of the signal path. The presence of a signal indicates a normal or non-alarm state. In the event of a break or other interruption in the signal path, the loss or diminution of the signal is detected and signifies an alarm condition. In the case of an optical fiber signal path, the optical fiber can be sensitive to incident nuclear radiation that causes a reduction in the amplitude and/or characteristics of the optical signal and which can be detected as an indication of an alarm condition.
Current fabrication techniques for installation of sensor sheets involve first applying a resin layer to the surface of the object to be enclosed, e.g., the interior walls of a cargo container or the outer surface of a pipeline. The resin must be allowed to dry to a certain point and then, within a specified time window, i.e., before the resin hardens, the sensor sheet is to be laid on top. A top layer of resin is thereafter applied and allowed to dry to hold fast the sensor sheet in a protective sandwich construction.
In some applications, for example, gas wells, it is not as much of an issue of security but, rather, one of locating a failure in order to quickly make a repair. Gas wells usually include a pipeline casing, however, when the casing is compromised and gas escapes through the ground to the surface, known as “surface casing vent flow and gas migration,” it must be repaired. The release of gas has to be stopped as soon as detected, and while it is relatively easy to detect that gas is leaking, identifying the location of the leak along the length of the casing is a much bigger challenge.
A known detection method runs an acoustic instrument down the well that detects noise patterns that are plotted on a graph as the instrument is slowly withdrawn. Any variances of sound, such as pitch, will be used to identify the location of the leak. When a leak location has been determined, a hole is made in the casing and cement is inserted in to stop the gas leak. The instrument, however, must be run again to assure that the hole has been plugged but a relatively large retry rate is necessary to finally seal the leak. The delays associated with this process of determining where the leak is located translate into lost operating time, the incurring of repair costs and, therefore, decreased revenue for the gas well operator.
There is, therefore, a need for providing a mechanism that will detect an intrusion or extrusion with respect to a pipeline container or enclosure and that can be applied quickly, easily and economically and that will be able to provide detection coverage for irregularly as well as regularly shaped volumetric enclosed structures. Additionally, determining a location of a defect is also needed in order to apply a repair.